Validation of PROMIS Physical Function Instruments in Patients With an Orthopaedic Trauma to a Lower Extremity

To evaluate the reliability, convergent validity, known-groups validity, and responsiveness of the Patient-Reported Outcomes Measurement Information System (PROMIS) Mobility Computer Adaptive Test (CAT) and PROMIS Physical Function 8a Short Form.

Prospective cohort study.

Two Level-I trauma centers.

Eligible adults with an isolated lower extremity trauma injury receiving treatment were approached consecutively (n = 402 consented at time 1, median = 80 days after treatment). After 6 months, 122 (30.3%) completed another assessment.

Cross-sectional and longitudinal monitoring of patients.

Floor and ceiling effects, reliability (marginal reliability and Cronbach's alpha), convergent validity, known-groups discriminant validity (weight-bearing status and fracture severity), and responsiveness (Cohen's d effect size) were evaluated for the PROMIS Mobility CAT, PROMIS Physical Function 8a Short Form, and 5 other measures of physical function.

PROMIS PFSF8a and Foot and Ankle Ability Measure Activities of Daily Living Index had ceiling effects. Both PROMIS measures demonstrated excellent internal consistency reliability (mean marginal reliability 0.94 and 0.96; Cronbach's alpha = 0.96). Convergent validity was supported by high correlations with other measures of physical function (r = 0.70-0.87). Known-groups validity by weight-bearing status and fracture severity was supported as was responsiveness (Mobility CAT effect size = 0.81; Physical Function Short Form 8a = 0.88).

The PROMIS Mobility CAT and Physical Function 8a Short Form demonstrated reliability, convergent and known-groups discriminant validity, and responsiveness in a sample of patients with a lower extremity orthopaedic trauma injury.